PERFORMANCE OF A LABORATORY CLEAN ROOM.

The performance of a small, 52 square meter laboratory clean room at the University of Minnesota has been evaluated using a system of aerosol measuring and monitoring instruments. Aerosol in the ambient atmosphere and in the clean room has been measured simultaneously using a condensation nucleus counter and diffusion battery, a differential mobility particle sizer and two laser optical particle counters to provide concentration and size distribution data between 0. 002 and 10 mu m diameters. The diurnal variation of the condensation nuclei concentration in the clean room has been found to follow closely that in the ambient atmosphere. This suggests that particles in the CNC range measured in the clean room have their origin in the ambient atmosphere and that the clean room filter does not provide a perfect shield between indoor and outdoor air for these small particles.